Ink composition for pressurized ball-point pen and pressurized ball-point pen

ABSTRACT

An ink composition for a pressurized ballpoint pen and a pressurized ballpoint pen which can exhibit excellent writing properties, do not cause ink leakage and which are suited to handwriting. The ink composition for a pressurized ballpoint pen includes at least a colorant, a solvent and silica, wherein a coagulated matter containing at least the silica is contained therein, and the ink composition has a viscosity of 10000 to 40000 mPa·s at 25° C. A pressurized ballpoint pen equipped with a refill, in which pressurized gas is charged into an ink reservoir charged with the ink composition for a pressurized ballpoint pen and a closed vessel containing the reservoir is also set forth.

TECHNICAL FIELD

The present invention relates to an ink composition for a pressurizedballpoint pen and a pressurized ballpoint pen, more specifically to anink composition for a pressurized ballpoint pen and a pressurizedballpoint pen which are excellent in a writing property and do not causeink leakage and which are suited to handwriting.

BACKGROUND ART

In general, known as a ballpoint pen are a gravity type (freeatmospheric type) ballpoint pen comprising a ballpoint pen tip, an inkreservoir and an ink filled thereinto and a so-called pressurized typeballpoint pen in which pressurized gas such as nitrogen gas is chargedinto an ink reservoir filled with an ink and a closed vessel containingit.

The above pressurized type ballpoint pen has the advantages that upwardwriting is possible and that an ink having a specific function can beused, but an ink reservoir charged with an ink is always pressurized, sothat a small amount of the ink is apt to leak from a pen tip.

In order to prevent the above matter, an apparent viscosity of an inkhas to be raised, and this brings about the problems that a writefeeling becomes heavier and it takes time to charge an ink reservoirwith an ink and that the ink is liable to be stuck onto the inside ofthe ink reservoir, that is, a so-called clear drain property isinferior.

On the other hand, it is described in Japanese Patent Publication No.48565/1972 that the main point is to prepare a writing instrument inwhich an ink or a fluid is not allowed to flow out in the vicinity of aball of the ballpoint pen tip in the form of a pressurized writing ormarking instrument, and disclosed therein is a ballpoint pen writinginstrument characterized by that a writing fluid for the above writinginstrument comprises at least one solvent, one colorant and at least onepolymer which is soluble in the above solvent and which can provide theabove fluid with a viscoelasticity, a strong coagulating property, astrong sticking property, a fluid resistance and a film-forming propertytogether with the other components for the writing fluid, wherein theabove writing fluid has a viscosity of 100000 cps or more (measured at25° C. and 0.3 rpm using a fifth cylindrical spindle in a Brookfield LMTviscometer), and a cross-linking carboxypolymethylene type polymer orpolyvinylpyrrolidone type polymer or both of them is used as the abovepolymer.

Further, a thixotropic ink for a pressurized ballpoint pen containinghigher fatty acid soap is disclosed in Japanese Patent ApplicationLaid-Open No. 096336/1975, and the viscosities of 600000 cps and 800000cps are given in the examples.

Further, an ink composition having metallic gloss which is set to aviscosity of 50000 cps or more is disclosed in Japanese PatentApplication Laid-Open No. 186574/1985. Also, an ink for a pressurizedballpoint pen used for a plotter is disclosed in Japanese PatentApplication Laid-Open No. 7775/1987, and it is described that theviscosity thereof falls preferably in a range of 40000 to 500000 cps.

However, any ink compositions for pressurizing disclosed in therespective official gazettes described above have a high viscosity, andthere still remain the problems described above, that is, the problemsthat an ink leaks from a pen tip is small amount; a write feelingbecomes heavier; it takes time to charge an ink reservoir with an ink;an ink is liable to be stuck onto the inside of an ink reservoir, and aso-called clear drain property is inferior, and so on.

On the other hand, an oil-based ink for a ballpoint pen containingsilica having a primary average particle diameter of 7 to 40 nm isdisclosed in Japanese Patent Application Laid-Open No. 195365/1998 whichis a prior art applied by the present inventors.

In the above prior art, however, it is described in the specificationthat “a pen body rises in a temperature when exposed to direct sunlightor an ink leaks from a pen tip in a certain case when left standingdownward for long time”, and it is a technique related to a gravity type(free atmospheric type) ballpoint pen. More specifically, it isdescribed that a content of silica is 0.01 to 2.0% by weight, preferably0.03 to 1.0% by weight, and it is 0.3% by weight, 1.0% by weight, 0.05%by weight and 0.5% by weight respectively in order in Examples 1 to 4. Asupplementary examination carried out by applying ballpoint pensspecifically described in Example 2 (1.0% by weight) and Example 4 (0.5%by weight) to pressurized ballpoint pens under the same conditions as inexamples described later has made it clear to bring about the problemthat an ink leaks from a pen tip. Further, observation of the aboveoil-based ink under an optical microscope has shown that coagulatedmatters containing silica are not found and that the ink stays in ahomogeneous state. Accordingly, the oil-based ink described in the aboveofficial gazette is different from the ink of the present invention inuses, recognition of the problems and ink physical properties.

In light of the problems on the conventional techniques described above,the present invention intends to solve them, and an object thereof is toprovide an ink composition for a pressurized ballpoint pen and apressurized ballpoint pen, wherein an ink is prevented from leaking froma pen tip; a write feeling is excellent; time for charging an inkreservoir with the ink can be shortened; and a clear drain property isexcellent as well.

BRIEF DESCRIPTION OF THE DRAWING

The drawing illustrates a pressurized ballpoint pen equipped with arefill in accordance with one aspect of the present invention.

DISCLOSURE OF THE INVENTION

Intensive investigations repeated by the present inventors on theconventional problems described above have resulted in successfullyachieving the object described above by an ink composition for apressurized ballpoint pen comprising at least a colorant, a solvent andsilica and a pressurized ballpoint pen charged with the above inkcomposition, wherein the above ink composition has a viscosity fallingin a specific range, and the physical properties fall in specificranges. Thus, the present applicant has come to complete the presentinvention.

That is, the present invention resides in the following items (1) to(7).

-   (1) An ink composition for a pressurized ballpoint pen comprising at    least a colorant, a solvent and silica, wherein a coagulated matter    containing at least silica is contained therein, and the ink    composition has a viscosity of 10000 to 40000 mPa·s at 25° C.-   (2) The ink composition for a pressurized ballpoint pen as described    in the above item (1), wherein the viscosity is 20000 to 35000 mPa·s    at 25° C.-   (3) The ink composition for a pressurized ballpoint pen as described    in the above item (1) or (2), wherein the coagulated matter    containing at least silica has a size of 1 to 100 μM.-   (4) The ink composition for a pressurized ballpoint pen as described    in any of the above items (1) to (3), wherein 10 or more coagulated    matters containing at least silica are observed in a range of 500    μm×500 μm under an optical microscope.-   (5) The ink composition for a pressurized ballpoint pen as described    in any of the above items (1) to (4), wherein silica has a specific    surface area of 80 m²/g or more measured by the BET method.-   (6) The ink composition for a pressurized ballpoint pen as described    in any of the above items (1) to (5), wherein the colorant contains    a pigment.-   (7) A pressurized ballpoint pen characterized by having a refill, in    which pressurized gas is charged into an ink reservoir charged with    the ink composition for a pressurized ballpoint pen as described in    any of the above items (1) to (6) and a closed vessel containing the    reservoir.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention shall be explained below indetails by invention.

The ink composition of the present invention for a pressurized ballpointpen is an ink composition comprising at least a colorant, a solvent andsilica, wherein a coagulated matter containing at least silica iscontained therein, and the ink composition has a viscosity of 10000 to40000 mPa·s at 25° C.

The colorant used in the present invention shall not specifically berestricted as long as it is a colorant used for a pressurized ballpointpen, and it includes a dye and a pigment.

The dye includes, for example, organic solvent-soluble dyes which areclassified into a solvent dye in a color index. The specific examples ofthe above solvent dye include Valifast Black 3806 (C. I. Solvent Black29), ditto 3807 (trimethylbenzylammonium salt of the dye of C. I.Solvent Black 29), Spirit Black SB (C. I. Solvent Black 5), Spiron BlackGMH (C. I. Solvent Black 43), Valifast Red 1308 (salt-forming matter ofthe dye of C. I. Basic Red 1 and the dye of C. I. Acid Yellow 23),Valifast Yellow AUM (salt-forming matter of the dye of C. I. BasicYellow 2 and the dye of C. I. Acid Yellow 42), Spiron Yellow C2 GH(organic acid salt of the dye of C. I. Basic Yellow 2), Spiron VioletCRH(C. I. Solvent Violet 8-1), Valifast Violet 1701 ((salt-formingmatter of the dye of C. I. Basic Violet 1 and the dye of C. I. AcidYellow 42), Spiron Red CGH (organic acid salt of the dye of C. I. BasicRed 1), Spiron Pink BH (C. I. Solvent Red 82), Nigrosine Base EX (C. I.Solvent Black 7), Oil Blue 603 (C. I. Solvent Blue 5), Neozapon Blue 808(C. I. Solvent Blue 70) and the like.

The pigment includes, for example, inorganic pigments such as carbonblack, graphite and titanium dioxide pigments, extender pigments such astalc, alumina, mica and alumina silicate, organic pigments such as azoor condensed azo base pigments, phthalocyanine base pigments,anthraquinone pigments, quinacridone pigments, isoindolinone basepigments, diketopyrrolopyrrole base pigments and various lake pigments,fluorescent pigments, pearl pigments and gold and silver metallicpigments.

Carbon black includes, for example, commercially available carbon blacksproduced by various production processes such as furnace black, channelblack and acetylene black, to be specific, Printex 75, Printex 60,Printex 45, Printex 35, Printex 25, Printex 200, Printex A, Printex G,Special Black 550, Special Black 350, Special Black 250, Special Black100, Lamp Black 101, Special Black 4, Printex U, Printex V (allmanufactured by Degussa AG), Monarch 900, Monarch 880, Monarch 800,Monarch 700, Regal 1660R, Regal 1500R, Regal 1415R, Regal 1300R, Regal1250R, Regal 1991, Elftex 8, Sterling R, Mogul-L (all manufactured byCabot Co., Ltd.), #1000, #900, MCF-88, MA7, MA8, #52, #45, #40, #33,#30, CF9 (all manufactured by Mitsubishi Chemical Corporation), Raven1500, Raven 1200, Raven 1170, Raven 1040, Raven 1000, Raven 890, Raven850, Raven 500, Raven 450, Raven 420, Raven 410, Paven H16, Raven H16,Raven H14, Royal Spevtra A and Neo Spevtra A Mark IV (all manufacturedby Columbian Co., Ltd.). However, it shall not be restricted to them.

Graphite can be used as a black pigment and a lubricant, and capable ofbeing used are graphites having various properties and sizes such asartificial graphite, natural graphite, scaly graphite, massive graphiteand soil-like graphite.

Various blue pigments can be used as the blue organic pigment andinclude, for example, C. I. Pigment Blue 15, 15:1, 15:2, 15:3, 15:4,15:6, 16, 17, 28, 29 and 36, and C. I. Pigment Blue 60, and they may betreated with a surfactant in the production step of the pigments.

In particular, the specific examples of the blue pigment includepigments such as Graphthol Blue 2GLS, Sandorin Blue RL and Sandorin Blue91052 manufactured by Clariant Co., Ltd., Lutetiacyanine CSNmanufactured by ICI Ltd., Palomar Blue B4806 and Palomar Blue B4707manufactured by Mobay Co., Ltd., Endurophtal Blue BT-788D manufacturedby Worlee Co., Ltd., Phthalocyanine Blue RS1517C manufactured byCappelle Co., Ltd., Heliogen Blue L6920, Heliogen Blue L6875F, HeliogenBlue L6901F, Heliogen Blue L6905F, Heliogen Blue L6975F, Heliogen BlueL6989F, Heliogen Blue L7072D, Heliogen Blue L7080, Heliogen Blue L7101Fand Heliogen Blue L6700F manufactured by BASF AG, Monastral Blue FBN,Monastral Blue CSN, Monastral Blue FNX and Monastral Blue RLmanufactured by Zeneca Co., Ltd., Catulia Cyanie L. PS manufactured byFrancolor Co., Ltd., Cyanine Blue B-7000, Cyanie Blue B-7800 and CyanieBlue B-8000 manufactured by Woo Snng Co., Ltd., Sunfast Blue 249-1282manufactured by Sun Co., Ltd., Catulia Cyanine 1. JS manufactured byFancolor Co., Ltd., Hpstaperm Blue BLF manufactured by Hoechst AG,Irgalite Blue GLNF, Irgalite Blue GLVD, Irgalite Blue ATC, CROMOPHTALBlue A3R, MICROLITH Blue 4G-WA and MICROLITH Blue 4G-A manufactured byCiba Specialty Chemicals Co., Ltd., Sovereign Blue 385, Holland Blue212, Kingfisher Blue 211 and Olympic Blue 190 manufactured by ShepherdCo., Ltd., Ultramarine Blue manufactured by Luh Co., Ltd., Blue EP37 andChromofine Blue 4920 manufactured by Dai Color Italy Co., Ltd.,Endurophtal Blue BT-729D manufactured by Worlee Co., Ltd., HeucosineBlue G1737, Heucosine Blue HS-5000 and Lackecht Blue G1737 manufacturedby Heubach Co., Ltd., Kenalake LFBRX manufactured by Kenalake Co., Ltd.,Chromofine Blue 4930, Chromofine Blue 5188 and Chromofine Blue SR5020manufactured by Dainichiseika Color & Chemicals MFG. Co., Ltd., FastogenBlue 5030L, Fastogen Blue 5420SD, Fastogen Blue 5502, Fastogen BlueTGR-F and Fastogen Blue EP-7 manufactured by Dainippon Ink & ChemicalsInc., Cyanine Blue G-134, Cyanine Blue SAS, Cyanine Blue KRS and CyanineBlue 4033 manufactured by Sanyo Shikiso Co., Ltd.

Various red pigments can be used as the red organic pigment and include,for example, C. I. Pigment Red 17, 144, 166, 170, 177, 202, 214, 220,254, 255, 264 and 272, and they may be treated with a surfactant in theproduction step of the pigments.

The commercially available specific trade names thereof include pigmentssuch as Chromophtal DPP RED BO, Chromophtal DPP RED BP, Chromophtal DPPRED DPP, Iragazin DPP Red BO, Iragazin DPP Red BTR, Chromophtal RED A2B, Chromophtal RED A 3B, Chromophtal Scarlet R, Chromophtal Scarlet RN,Chromophtal Scarlet BR, Chromophtal Red BRN and Cinquasia Magenta TR235-6 manufactured by Ciba Specialty Chemicals Co., Ltd., Dainichi FastPoppy Red G and Dainichi Fast Poppy Red R manufactured by DainichiseikaColor & Chemicals MFG. Co., Ltd., Bayerrox Red 110M, Bayerrox Red 120MNand Bayerrox Red 130M manufactured by Bayer AG, Toluidine Red G G0335C,Toluidine Red RN0333C, Bonitol Red BM, Bonitol Red 4844C, Lysopac Red4841C, Cappoxyt Red 4435B, Cappoxyt Red 4437B, Mineral Orange ThiosolGL, Mineral Orange Thiosol G, Mineral Orange Solipur GH, Mineral RedSolipur 3BH and Lysopac Red 7030C manufactured by Cappelle Co., Ltd.,Copperas Red R9998 manufactured by Hercos Co., Ltd., Sicored L3750,Lithol Scharlach L4301, Litholechtmaroon L4763, Sicoflush-P-Maroon 4763,Paliogen Red Violet L5080, Sicotrans Red L2817, Sicomin Red L3025,Sicomin Red L3230s and Sico Fast Scarlet L4252 manufactured by BASF AG,Heucotron Red 230, Paliogen Red 3880HD, Paliogen L3920 and Paliogen RedL4210 manufactured by Heubach Co., Ltd., Horna Molybdator. MLN-74-SQ,Horna Molybdator. MLH-74-Q and Irgalite Red 3RS manufactured by CibaSpecialty Chemicals Co., Ltd., Toluidine Red L, Toluidine Red K, Bon RedSR, Bon Red 3M, Bon Red MP, Fast Bordeaux C, Lake Red C-900, Fast RedFGR and Chromophtal Red A2B and Chromophtal Red A3B manufactured by WooSung Co., Ltd., Novoperm Red Violet MRS new, Permanent Bordeaux FGR,Permanent Red FGR70, Hostaperm Rosa E and Novoperm Reel F3RK70manufactured by Hoechst AG, Quindo Magenta RV6832 manufactured by MilesCo., Ltd., Perrindo Maroon R6422 manufactured by Bayer Mobay Co., Ltd.and Grapbhol Red 5BLS manufactured by Sandoz Co., Ltd.

Various yellow pigments can be used as the yellow organic pigment andinclude, for example, C. I. Pigment Yellow 1, 3, 12, 13, 14, 16, 17, 55,81, 83, 74, 93, 94, 95, 97, 109, 110, 120, 128, 138, 147, 154, 155, 167,185 and 191, and they may be treated with a surfactant in the productionstep of the pigments.

The commercially available specific trade names thereof include pigmentssuch as Paliotol Yellow 2140HD, Sicopal Yellow L1110, Sicotan YellowL1912, Sicomin Yellow L1622, Sicomin Yellow L1630S, Sicomin YellowL1635S, Sicotrans Yellow L1916, Sico Yellow 1252HD, Paliogen YellowL1482, Paliogen Yellow L1560, Paliotol Yellow D1155 and Paliotol YellowL0960HD manufactured by BASF AG, Horna Chrome Yellow GMX AX-15, HornaChrome Yellow GMXAH-35, Horna Chrome Yellow GU-15-SQ, Irgazin Yellow GO,Irgazin Yellow 2RLT, Irgazin Yellow 3RLTN, Irgazin Yellow 5GLT and,Irgazin Yellow 2GLTE manufactured by Ciba Specialty Chemicals Co., Ltd.,Bayferrox 915, Bayferrox 920, Bayferrox 3420, Bayferrox 3910 andBayferrox 3920 manufactured by Bayer AG, Novoperm Yellow H2G, HostapermYellow H4G, Hostaperm Yellow H3G, Hostaperm Yellow H6G, Novoperm YellowF2G and Novoperm Yellow HR70 manufactured by Hoechst AG, Pigment Yellow1717, Pigment Yellow 1450, Pigment Yellow 1710, Pigment Yellow 1711,Pigment Yellow 1707, Pigment Yellow 8104, Pigment Yellow 1425 and lightFast Pigment Yellow R manufactured by Sanyo Shikiso Co., Ltd., SEIKAFAST YELLOW 10HG, SEIKA FAST YELLOW A-3, SEIKA FAST YELLOW 2035, SEIKAFAST YELLOW 2054, SEIKA FAST YELLOW 2300, SEIKA FAST YELLOW 2200, SEIKAFAST YELLOW 2270, SEIKA FAST YELLOW 2400(B), SEIKA FAST YELLOW 2500,SEIKA FAST YELLOW 2600, SEIKA FAST YELLOW ZAY-260, SEIKA FAST YELLOW2700(B) and SEIKA FAST YELLOW 2770 manufactured by Dainichiseika Color &Chemicals MFG. Co., Ltd., Sandrin Yellow $G, PV Fast Yellow HGR,Novoperm Yellow FGL, Novoperm Yellow H10G01, HANSA Yellow 10G, PV FastYellow H2G-01 and Permanent Yellow NCG manufactured by Clariant Co.,Ltd.

Various green pigments can be used as the green organic pigment andinclude, for example, C. I. Pigment Green 7, 17, 36, 50 and 70, and theymay be treated with a surfactant in the production step of the pigments.

The commercially available specific trade names thereof include pigmentssuch as Chromofine Cyanine Green 2GN, Chromofine Cyanine Green 5301,Chromofine Cyanine Green 2GN, Chromofine Cyanine Green 537, DainichiCyanine Green FG, Dainichi Cyanine Green FGH and Chromofine Green 5370manufactured by Dainippon Ink & Chemicals Inc., Fastogen Green 5005,Fastogen Green 5710, Fastogen Green B, Fastogen Green S, Fastogen GreenSF, Fastogen Green SO and Fastogen Green 2YK manufactured byDainichiseika Color & Chemicals MFG. Co., Ltd., Heliogen Green 8680,Heliogen Green 8681K, Heliogen Green 8682T, Heliogen Green 8730,Heliogen Green 8730K, Heliogen Green A, Heliogen Green GNA, HeliogenGreen G, Heliogen Green GA, Heliogen Green GN, Heliogen Green GTA,Heliogen Green GV, Heliogen Green GWS, Heliogen Green K 8730, HeliogenGreen L 8730, Fastgen Green MY, Fastgen Green YCN, Helio Fast Green GT,Heliogen Green 6G, Heliogen Green 6GA, Heliogen Green 8GA, HeliogenGreen 9360, Heliogen Green K9360, Heliogen Green L9140 and HeliogenGreen L9361 manufactured by BASF AG, Iragalite Fast Brilliant Green 3GL,Iragalite Fast Brilliant Green GL, Iragalite Green GLN and IragaliteGreen 6G manufactured by Ciba Specialty Chemicals Co., Ltd., LiofastGreen B237, Lionol Green B201, Lionol Green Y102, Lionol Green YS07,Lionol Green 2Y301, Lionol Green 2YS, Lionol Green 6YK and Lionol Green6YKPCN manufactured by Toyo Ink MFG. Co., Ltd., Polymo Green FBH, PolymoGreen FGH, Polymo Green 6G, Polymo Green G, Polymo Green GN and PolymoGreen GN500 manufactured by Polymon Developments Ltd., Sanyo CyanineGreen, Sanyo Cyanine Green F6G, Sanyo Phthalocyanine Green F6G, SanyoPhthalocyanine Green FB, Sanyo Phthalocyanine Green FB Pure, SAX, SAX(pigment) and Sanyo Phthalocyanine Green 6YS manufactured by SanyoShikiso Co., Ltd.

Various kinds of usual titanium oxide and fine particle titanium oxidecan be used as the inorganic extender pigments. In addition thereto,talc and the like can be used.

The dyes and pigments described above may be used alone or in a mixtureof two or more kinds thereof as the colorant used in the presentinvention, and the pigment preferably may be contained in the colorantfrom the viewpoint of exhibiting the brilliant drawn line density.

A content of the above colorants is preferably 10 to 60% by weight, morepreferably 20 to 50% by weight in total based on the whole amount of theink composition.

In a condition when a content of the above colorants is less than 10% byweight, the trouble that the drawn line density is low is caused. On theother hand, in a condition when a content of the above colorants is morethan 60% by weight, the fluidity and the solubility of the dissolvedcomponents are lowered, and the storage stability is also lowered.Accordingly, both of the above conditions are not preferred.

Silica used in the present invention is added in order to form acoagulated matter containing at least silica in the ink compositionwithout exerting an adverse effect on the writing property and the cleardrain property to prevent the ink from leaking in the pressurizedballpoint pen.

Silica which can be used is particularly preferably anhydrous silica,and to be specific, it includes 50, 90G, 130, 200, 200V, 200CF, 200FAD,300, 300CF, 380, 972R, 972V, R972CF, R974, R202, R805, R812, R812S,OX50, TT600, RX200, RY200 and MOX80 and MOX170 which are mixtures ofRY200 and AL203 manufactured by Nihon Aerosil Co., Ltd., L90, LM-130,LM-5, M-5, M-5P, PTG, MS-55, MS-75, HS-5, EH-5, TS-530, TS-610 andTS-720 manufactured by CABOT Co. Ltd.

Preferred silica has a specific surface area of 80 m²/g or more measuredby the BET method, and particularly preferred silica has a specificsurface area of 200 m²/g or more and 450 m²/g or less.

A content of the above silicas is 0.5 to 5% by weight, preferably 1 to3% by weight and more preferably 2.0 to 2.5% by weight based on thewhole amount of the ink composition.

If a content of the above silica is less than 0.5% by weight, the inkleaking-preventing effect is reduced. On the other hand, if it exceeds5% by weight, a viscosity of the ink becomes very high. Therefore, insaid silica content regions, the ballpoint pen is unfavorable inhandwriting. Accordingly, the said regions are not preferred.

The organic solvent used in the present invention is added forcontrolling the viscosity, accelerating dissolution of the dye,controlling dispersion of the pigment and controlling a drying propertyof the ink.

The organic solvent which can be used includes, for example, glycolsolvents such as ethylene glycol, diethylene glycol, propylene glycol,dipropylene glycol, hexylene glycol and the like, ether solvents such asethylene glycol monomethyl ether, ethylene glycol monoethyl ether,ethylene glycol monobutyl ether, 3-methyoxybutanol, ethylene glycolmonohexyl ether, ethylene glycol monophenyl ether, diethylene glycolmonomethyl ether, diethylene glycol monoethyl ether, diethylene glycolmonobutyl ether, diethylene glycol monohexyl ether, diethylene glycolmonophenyl ether, propylene glycol monomethyl ether, propylene glycoln-propyl ether, propylene glycol n-butyl ether, propylene glycolmonoethyl ether, dipropylene glycol n-propyl ether, propylene glycolmono-n-butyl ether, propylene glycol monophenyl ether, dipropyleneglycol monomethyl ether, dipropylene glycol monoethyl ether, dipropyleneglycol n-butyl ether, dipropylene glycol monophenyl ether, tripropyleneglycol monomethyl ether, tripropylene glycol monoethyl ether,tripropylene glycol n-butyl ether, propylene glycol methyl etheracetate, propylene glycol diacetate, dipropylene glycol dimethyl ether,tripropylene glycol monophenyl ether and the like, alcohol solvents suchas benzyl alcohol, α-methylbenzyl alcohol and the like, propylene glycolmethyl ether acetate, propylene glycol diacetate,N-methyl-2-pyrrolidone, rosin alcohol, water (refined water,ion-exchanged water, purified water and deep marine water) and the like.The above solvents can be used alone or in a mixture of two or morekinds thereof.

A content of the above solvents is preferably 30 to 80% by weight, morepreferably 35 to 60% by weight based on the whole amount of the inkcomposition.

Further, in the present invention, various resins can be added forraising the fixing property, preventing strike-through of the drawnlines, a function as a dispersant for the pigment and the like,controlling the viscosity and accelerating dissolution of the dye.

The resins which can be used include, for example,toluenesulfonamide-epoxy resins, condensed resins of ketones such ascyclohexanone, acetophenone, urea and the like with formaldehyde,condensed resins of cyclohexanone and resins obtained by hydrogenatingthese resins, maleic acid resins, copolymers of styrene and maleic acidester, copolymers of styrene and acrylic acid or esters thereof,polyvinylpyrrolidone, polyvinylbutyral, polyvinylacetal, polyamideswhich are the condensed resins of polymer fatty acids and polyamines,epoxy resins, polyvinyl alkyl ethers, coumarone-indene resins,polyterpenes, terpene resins, terpene-phenol resins, xylene resins,rosin base resins and hydrogenated resins thereof, rosin-modified maleicacid resins, vinylpyrrolidone-vinyl acetate copolymers,polymethacrylates, polyacrylic acid-polymethacrylic acid copolymers,polyoxyethylene and phenol resins. The above resins can be used alone orin a mixture of two or more kinds thereof.

A content of the above resins is preferably 0 to 30% by weight, morepreferably 1 to 25% by weight based on the whole amount of the inkcomposition.

Further, the ink composition of the present invention for a pressurizedballpoint pen may further comprise a lubricant selected from the groupconsisting of the higher fatty acid, metallic soap, a phosphoric acidester base lubricant, a nonionic surfactant having a long chain alkylgroup or the like. In particular, oleic acid may be most suitablycomprised therein. Further, suitable surfactants, dispersants and thelike may also be comprised therein if necessary.

In the present invention, the viscosity has to be controlled to 10000 to40000 mPa·s, preferably 20000 to 35000 mPa·s at 25° C. in terms ofpreventing the ink from leaking from the pen tip, elevating the writefeeling, further shortening time to charge the ink reservoir with theink and further raising the clear drain property.

If a condition when the above viscosity exceeds 40000 mPa·s, the writefeeling becomes heavier, and it becomes difficult to smoothly write. Onthe other hand, in a condition when the viscosity is less than 10000mPa·s, no problems are caused in the beginning, but as time passes,leaking of the ink is liable to be caused. Accordingly, both of theseconditions are not preferred.

The ink composition of the present invention for a pressurized ballpointpen can be produced by applying a conventionally known productionprocess for an ink composition using the respective components describedabove. That is, the ink composition and the like for a pressurizedballpoint pen can be obtained by dissolving the respectivesolvent-soluble components by means of a stirring mixer. When using thepigment and the like, the pigment is dispersed together with thedispersant and the other components by means of a dispersing mixer, andthen the necessary components are added and mixed, whereby the inkcomposition for a pressurized ballpoint pen can be obtained.

In the production, heating can be applied in order to dissolve the solidmatters such as the dye and the like, and a filter and a centrifugalseparator can be used, if necessary, in order to remove coarse particlesof the organic pigment and the like.

In the present invention, the size and the number of the coagulatedmatters of silica can be controlled by, for example, a length ofstirring time and a stirring power and the like. They can be controlledas well by making use of a dispersing apparatus and an emulsifyingapparatus. A roll mill can be used for the ink composition of thepresent invention for a pressurized ballpoint pen since the compositionis viscous.

The silica-coagulated matters contained in the ink composition of thepresent invention have a size of preferably 1 μm or more, and this makesit possible to efficiently prevent the ink from leaking from the pentip. If the above coagulated matters of silica having a size ofexceeding 200 μm are present in the form of a bulk, the ink is preventedfrom leaking, but a scratch feeling is liable to be brought about orsome ink-squeezeout is liable to be caused. Therefore the size of thecoagulated matters of silica is preferably 1 to 100 μm, but those sizeof 200 μm or more is unfavorable.

The number of the coagulated matters of silica as well as the range ofthe size described above is influenced and varied by a content ofsilica, a ball diameter at a pen tip, a clearance thereof and the like.It can be confirmed in the field of view of 500 μm×500 μm in an opticalmicroscope, and if 10 or more bulks of the above coagulated matters canbe observed in the said field, the ink can be prevented from leakingfrom the pen tip without causing any problems in terms of actual use. Itis preferably controlled to 10 to 300 bulks.

The pressurized ballpoint pen of the present invention is charged withthe ink composition of the present invention for a pressurized ballpointpen, and the pressurized ballpoint pen structure shall not specificallybe restricted as long as it is a ballpoint pen structure of apressurized type. As may been seen from the drawing, a preferredpressurized ballpoint pen 1 is equipped with a refill 2 in whichpressurized gas 3 such as nitrogen gas is charged into an ink reservoir4 charged with the ink 5 and a closed vessel 6 containing the reservoir.

The ink composition of the present invention for a pressurized ballpointpen thus constituted does not cause, though it does not have a very highviscosity, ink leaking from the pen tip as is observed in the priorarts. This is estimated to be attributable to the fact that thecontrolled bulks of silica which are dispersed in the ink plug up theclearance part which is the ink flow part, whereby the ink is preventedfrom leaking from the pen tip. The individual coagulated particles areaggregates of very small particles and therefore easily broken byrotation of the ball at the pen tip, whereby the ink flows out withoutany problems to make it possible to write.

The ink composition of the present invention for a pressurized ballpointpen contains a viscous and adhesive resin in a blend composition, andthe colorant is dissolved or finely dispersed. Accordingly, the inkquickly penetrates into a paper face to form beautiful drawn lines, sothat the lines written on the paper face can not be erased by an eraser.

In the pressurized ballpoint pen of the present invention equipped witha refill in which pressurized gas is charged into an ink reservoircharged with the ink composition of the present invention for apressurized ballpoint pen and a closed vessel containing the reservoir,the ink does not leak as shall be verified in examples described laterto exhibit an excellent writing property and refill ink remaining amountvisibility (clear drain property).

EXAMPLES

Next, the present invention shall be explained in further details withreference to examples and comparative examples, but the presentinvention shall not be restricted at all by the examples describedbelow.

Examples 1 to 8 and Comparative Examples 1 to 6

Ink compositions having blend compositions shown in the following Table1 and Table 2 were prepared by the following method.

In preparing the respective ink compositions, a pigment was firstdispersed by means of a three roll mill or a bead mill using a part of aresin and a solvent out of the components as a dispersant, and thedispersions were transferred to a vessel equipped with a refluxcondenser and a stirrer. Then, a part of the other components was addedthereinto, and the mixtures were stirred at 60° C. for 5 hours.Thereafter, a prescribed amount of silica was added thereinto, and themixtures each were treated by the following respective treating methods,and the remainders were added and stirred to prepare ink compositions.

A viscosity of the respective ink compositions was measured by means ofa corn plate type viscometer (TV-20 type, manufactured by Tokimec Inc.,standard corn: 1 rpm, rate of shear: 3.84 s⁻¹). The values of theviscosities in Table 1 are shown in terms of 1/100, and therefore theactual values thereof have to be magnified by 100 times in Example 1 andfollowing Examples (for example, 31200 mPa·s in Example 1).

In the course of preparing the inks, the inks each were sampled in duecourse to observe them under a microscope having 10 (an ocular side)×10(an objective side) magnification (manufactured by Nicon Co., Ltd,hereinafter the same shall apply) to observe the bulks of silica, andthey were controlled so that the size and the numbers which were suitedin the present invention were obtained, whereby the inks were prepared.The individual inks were prepared by the following detailed productionprocess.

Example 1 Black Ink

After adding silica, the components were passed once through a threeroll mill and recovered, and the remainder was added thereinto toprepare an ink.

Example 2 Black Ink

After adding silica, the components were passed once through the threeroll mill and recovered, and the remainder was added thereinto toprepare an ink.

Example 3 Black Ink

After adding silica, the components were passed once through the threeroll mill and recovered, and the remainder was added thereinto toprepare an ink.

Example 4 Red Ink

After adding silica, the components were passed twice through the threeroll mill and recovered, and the remainder was added thereinto toprepare an ink.

Example 5 Red Ink

After adding silica, the components were stirred while cooling at 5000rpm for one hour by means of a homomixer (T. K. homomixer; manufacturedby Tokushu Kiko Kogyo Co., Ltd.) and then recovered, and the remainderwas added thereinto, stirred and mixed to prepare an ink.

Example 6 Blue Ink

After adding silica, the components were stirred while cooling at 5000rpm for one hour by means of the homomixer (T. K. homomixer;manufactured by Tokushu Kiko Kogyo Co., Ltd.) and then recovered, andthe remainder was added thereinto, stirred and mixed to prepare an ink.

Example 7 Purple Ink

After adding silica, the components were stirred while cooling at 5000rpm for one hour by means of the homomixer (T. K. homomixer;manufactured by Tokushu Kiko Kogyo Co., Ltd.) and then recovered, andthe remainder was added thereinto, stirred and mixed to prepare an ink.

Example 8 Blue Black Ink

After adding silica, the components were stirred while cooling at 2500rpm for 5 hours by means of a high speed stirrer (T. K. homodisper;manufactured by Tokushu Kiko Kogyo Co., Ltd.) and then recovered, andthe remainder was added thereinto, stirred and mixed to prepare an ink.

Comparative Example 1 Black Ink

The pigment and all the remaining materials which were subjected inadvance to dispersing treatment were mixed and stirred for 5 hours, andthe mixture was passed 5 times through the three roll mill and thenrecovered, followed by adding the remainder to prepare an ink.

Comparative Example 2 Red Ink

The pigment and all the remaining materials which were subjected inadvance to dispersing treatment were mixed and stirred for 5 hours, andthe mixture was passed 5 times through the three roll mill and thenrecovered, followed by adding the remainder to prepare an ink.

Comparative Example 3 Blue Ink

After adding silica, the components were stirred while cooling at 5000rpm for one hour by means of the homomixer (T. K. homomixer;manufactured by Tokushu Kiko Kogyo Co., Ltd.) and then recovered, andthe remainder was added thereinto, stirred and mixed to prepare an ink.

Comparative Example 4 Black Ink

After adding silica, the components were stirred while cooling at 500rpm for 5 hours by means of the high speed stirrer (T. K. homodisper;manufactured by Tokushu Kiko Kogyo Co., Ltd.) and then recovered, andthe remainder was added, stirred and mixed to prepare an ink.

Comparative Example 5 Black Ink

An ink was prepared according to a production process shown in Example 2described in Japanese Patent Application Laid-Open No. 195365/1998.

Comparative Example 6 Red Ink

An ink was prepared according to a production process shown in Example 4described in Japanese Patent Application Laid-Open No. 195365/1998.

The ink compositions obtained in Examples 1 to 8 and ComparativeExamples 1 to 6 described above were measured for the presence of thesilica-coagulated matter bulks and the approximate number thereof by thefollowing method. Further, the pressurized ballpoint pens wereevaluated, that is, a writing property at 15° C., an ink leakage testand a refill ink remaining amount visibility were evaluated. The resultsthereof are shown in the following Table 1 and Table 2.

Measuring method of the presence of the silica-coagulated matter bulksand the approximate number thereof.

The inks were observed under a microscope having 10×10 magnification (anocular side×an objective side) to take the photos of the states of therespective inks. A plotting film of 0.05×0.05 mm was put on the samplesto measure an area.

The presence of the individual silica-coagulated matter bulks and theapproximate size thereof were measured by an object microscale (minimumscale: 10 μm).

A slide glass and a cover glass used are ones used in a usual biologicalmicroscope, and the samples have an almost constant thickness, so thatno specific problems are involved therein. When the samples are preparedin more accurate thickness, a blood cell calculating board and abacterial calculating board which have a constant depth may be used.

The red, blue, purple and blue black inks prepared in Examples 4 to 8and Comparative Examples 2 and 3 could be observed directly under amicroscope. However, the black inks prepared in Examples 1 to 3 andComparative Examples 1, 4 and 5 were liable to be short of a lightquantity. Accordingly, an ink weight on the slide glass was measured,and the same amount of a solvent was added thereinto and slightly mixedby means of a pin and the like. Then, the samples were observed. In theabove case, the number of the bulks was doubled after counting.

Evaluation Method of Pressurized Ballpoint Pen

The respective ink compositions 0.3 ml prepared in the respectiveexamples and comparative examples described above were charged and thenassembled into SJP-7 manufactured by Mitsubishi Pencil Co., Ltd. in thestate that a pressure of approximate 3000 hpa was maintained by nitrogengas to prepare pressurized oil-based ballpoint pens for test, and theywere used for a writing property test and an ink leakage test.

Writing Property Test Method:

The respective pressurized ballpoint pens for a test obtained above wereused for writing on a writing paper by a free hand to evaluate asmoothness and a lightness of a write feeling according to the followingevaluation criteria.

Evaluation Criteria:

-   ⊚: very smooth and light write feeling-   ◯: smooth and light write feeling-   Δ: write feeling slightly short of smoothness and lightness-   ΔΔ: a little heavy write feeling-   x: very heavy write feeling    Ink Leakage Test Method:

In the ink leakage test, the respective pressurized ballpoint pens for atest were subjected to waste writing and then left standing at atemperature of 25° C. and a humidity of 60% for 7 days with a pen tipturning downward to measure an amount of the ink leaking from the pentip, and the most frequent value in the ten samples was taken andevaluated according to the following evaluation criteria.

Evaluation Criteria:

-   ⊚: ink leakage is not observed at all-   ◯: a very small amount of ink leakage is observed at pen tip-   Δ: a middle amount of ink leakage is observed at pen tip-   ΔΔ: a large amount of ink leakage is observed at pen tip-   x: ink leaks and drops    Visibility Evaluating Method for Refill Ink Remaining Amount in    Pressurized Ballpoint Pen:

The respective inks prepared were charged into a refill comprising apolypropylene tube (treated an inside thereof with silicone) and astainless tip (ball made of cemented carbide and having a diameter of0.7 mm), and then it was subjected to a writing test in the state that apressure of approximate 3000 hpa was maintained by nitrogen gas appliedfrom the rear part of a refill. After writing 500 m, a sticking state ofthe ink onto the inside of the polypropylene tube in the ink-consumingpart was visually evaluated according to the following evaluationcriteria.

Evaluation Criteria:

-   ⊚: ink is not stuck at all-   ◯: a very small amount of ink is observed to be stuck-   Δ: ink is observed to be stuck in a circle form-   ΔΔ: ink is observed to be continuously stuck upward and downward-   x: ink is observed to be stuck in almost all area and whole    circumference

TABLE 1 (blend unit: % by weight, total 100 %) Example 1 2 3 4 5 6 7 8Colorant: (drawn line color, Black Black Black Red Red Blue Purple BBBB: blue black) C. I. Pigment Red 254 10 C. I. Pigment Red 255 7 C. I.Pigment Blue 60 8 7 7 Carbon black*1 7 7 Soil-like graphite*2 5Nigrosine Base EX*3 22 20 22 6 Aizen Spiron Violet C-RH*4 10 10 10 5 3.53.5 Aizen Spiron Yellow C-2GH*4 5 Aizen Spiron Yellow C-GNH*4 5 5 5 5Aizen Spiron Red C-GH*4 10 15 17 Aizen S.B.N. Blue 701*4 10 10 Solvent:Benzyl alcohol 33.5 43 33 29 32.3 41 37 36.5 2-Phenoxyethanol 20 16Dipropylene glycol 10 10 10 Ethylene glycol monobenzyl 10 10 etherResin: Polyvinylbutyral resin*5 2.5 5 4 5 5 5 Synthetic Resin*6 4 4 1513 14 14 10 Rosin alcohol*7 5 Polyvinylpyrrolidone (K-90)*8 1.5 1 1 11.5 1.5 1.5 1.5 Silica (Aerosil 380)*9 2.5 2 1.5 2 2.2 2.5 2 2.5 Othercomponents: Oleic acid 8 8 5 3 2 3 3 3 Polyoxyethylenedodecylamine*10 1Phosphoric acid ester 1.5 1 Presence of silica-coagulated PresentPresent Present Present Present Present Present Present matter bulk of1μm or more Approximate number of silica- 212 or 104 or 28 or 38 or 31or 40 or 40 or 95 or coagulated bulk (falling in a more more more moremore more more more range of 500 × 500 μm) Viscosity (mPa·s × 100, at25° C.) 312 220 180 360 330 325 198 320 Writing property (at 150 ° C.) ⊚⊚ ⊚ ◯ ⊚ ⊚ ⊚ ⊚ Ink leakage test ⊚ ⊚ ◯ ⊚ ⊚ ⊚ ◯ ⊚ Refill ink remainingamount ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ visibility

TABLE 2 (blend unit: % by weight, total 100 %) Comparative Example 1 2 34 5 6 Colorant: Black Red Blue Black Black Red C. I. Pigment Red 254 10C. I. Pigment Blue 60 8 Carbon black*1 7 7 Nigrosine Base EX*3 20 20Valifast Black #1802*3 15 Aizen Spiron Violet C-RH*4 10 5 10 10 AizenSpiron Yellow C-2GH*4 5 5 Aizen Spiron Yellow C-GNH*4 5 STP Orange 6*315 Valifast Yellow AUM*4 5 Aizen Spiron Red C-GH*4 10 4 Aizen Spiron RedC-BH*4 4 Aizen S.B.N. Blue 701*4 10 Solvent: Benzyl alcohol 37 30 4840.5 10 10 2-Phenoxyethanol 22 42.5 37.5 Dipropylene glycol 10 Resin:Polyvinylbutyral resin*5 10 4 2 3.5 Synthetic Resin*6 13 10 3 Ketoneresin*11 13 Polyvinylpyrrolidone (K-90)*8 1 1 1.5 1 1Polyvinylpyrrolidone (K-30)*12 25 Silica (Aerosil 380)*9 2 2 2.5 2 0.50.5 Silica (Aerosil 200)*13 1 Other components: Oleic acid 8 3 3 8 3 3Presence of silica-coagulated None None Present Present None None matterbulk of 1 μm or more Approximate existing number of 0 0 92 or Refer to 00 silica-coagulated bulk (in a range of more remark 500 x 500 μm)Viscosity (mPa·s × 100, at 25° C.) 1015 321.5 78 435 85 162 Writingproperty (at 15° C.) X ◯ Δ ΔΔ ◯ ΔΔ Ink leakage test X X X ⊚ X X Refillink remaining amount X ◯ ◯ ΔΔ ◯ ΔΔ visibility Remark: 2 bulks of 200 μmor more and 30 bulks of the other sizes were observed in ComparativeExample 4.

*1 to *13 in Table 1 and Table 2 mean the following:

-   *1: MA8 manufactured by Mitsubishi Chemical Corporation-   *2: Soil-like graphite T-1 manufactured by Nippon Graphite    Industries Ltd.-   *3: manufactured by Orient Chemical Industries Ltd.-   *4: Alcohol-soluble dye, manufactured by Hodogaya Chemical Co., Ltd.-   *5: S-Lec B BL-1, manufactured by Sekisui Chemical Co., Ltd.-   *6: Synthetic Resin SK, manufactured by Huels AG-   *7: ABITOL, manufactured by Hercules Incorporated-   *8: PVP K90, manufactured by ISP Co., Ltd.-   *9: Aerosil 380, the BET specific surface area: 380 m²/g,    manufactured by Nihon Aerosil Co., Ltd.-   *10: Nimine L202, manufactured by Nihon Oil & Fat Corporation-   *11: Hilac #111, manufactured by Hitachi Chemical Co., Ltd.-   *12: PVP K30, manufactured by ISP Co., Ltd.-   *13: Aerosil 200, the BET specific surface area: 200 m²/g,    manufactured by Nihon Aerosil Co., Ltd.

As apparent from the results shown in Table 1 and Table 2 describedabove, it was found out that the ink compositions for a pressurizedballpoint pen each prepared in Examples 1 to 8 falling in the scope ofthe present invention are prevented from leaking from the pen tip andare excellent in a write feeling as well as a clear drain property ascompared with those prepared in Comparative Examples 1 to 6 fallingoutside the scope of the present invention.

In Examples 1 to 8 and Comparative Example 3, observation of the size ofthe silica-coagulated matters resulted in finding that it fell in arange of 1 to 100 μm. In Comparative Example 3, the ink leaked since theviscosity was less than 10000 mPa·s, and the writing property wasinferior. In Comparative Example 4, the size of the silica-coagulatedmatters exceeded 200 μm in some matters, and the viscosity exceeded40000 mPa·s, so that the writing property and the remaining amountvisibility were inferior.

Further, Comparative Examples 5 and 6 are Example 2 (silica content:1.0% by weight) and Example 4 (silica content: 0.5% by weight) eachspecifically described in Japanese Patent Application Laid-Open No.195365/1998. In these cases, it was found out that the silica-coagulatedmatters are not prepared and the inks stay in a homogeneous state, sothat brought about is the problem that the inks leak from the pen tips.

INDUSTRIAL APPLICABILITY

According to the present invention, provided are an ink composition fora pressurized ballpoint pen and a pressurized ballpoint pen which canprevent an ink from leaking from a pen tip and are excellent in a writefeeing and which can shorten time for charging an ink reservoir with theink and are excellent as well in a clear drain property.

1. An ink composition for a pressurized ballpoint pen comprising atleast a colorant, a solvent and 0.5 to 5 wt% silica having a specificsurface area of 80 m^(2/)g or more measured by the BET method, wherein acoagulated matter containing at least the silica is contained therein,said the coagulated matter having size of 1 to 200 μm and the inkcomposition has a viscosity of 10000 to 40000 mPa·s at 25°.
 2. The inkcomposition for a pressurized ballpoint pen as described in claim 1,wherein the coagulated matter containing at least silica has a size of 1to 100 μm.
 3. The ink composition for a pressurized ballpoint pen asdescribed in claim 2, wherein 10 or more coagulated matters containingat least silica are observed in a range of 500 μm×500 μm under anoptical microscope.
 4. A pressurized ballpoint pen equipped with arefill, in which pressurized gas is charged into an ink reservoircharged with the ink composition for a pressurized ballpoint pen asdescribed in claim 3 and a closed vessel containing the reservoir.
 5. Apressurized ballpoint pen equipped with a refill, in which pressurizedgas is charged into an ink reservoir charged with the ink compositionfor a pressurized ballpoint pen as described in claim 2 and a closedvessel containing the reservoir.
 6. The ink composition for apressurized ballpoint pen as described in claim 1, wherein 10 or morecoagulated matters containing at least silica are observed in a range of500 μm×500 μm under an optical microscope.
 7. A pressurized ballpointpen equipped with a refill, in which pressurized gas is charged into anink reservoir charged with the ink composition for a pressurizedballpoint pen as described in claim 6 and a closed vessel containing thereservoir.
 8. A pressurized ballpoint pen equipped with a refill, inwhich pressurized gas is charged into an ink reservoir charged with theink composition for a pressurized ballpoint pen as described in claim 1and a closed vessel containing the reservoir.